Sound-dampening pump



March 7, 1961 L. G. L. THOMAS SOUND-DAMPENING PUMP Filed July 3. 1959 oygj ZZZ SOUND-DAMPENING PUMP Louis G. L. Thomas, Merion Station, Pa., assignor to C. H. Wheeler Manufacturing Company, Philadelphia, Pa., a corporation of Pennsylvania Filed July 3, 1959, Ser. No. 824,890

Claims. (Cl. 103-114) The invention relates to centrifugal pumps and is particularly concerned with dampening the noise of operation.

Sounds which are transmitted from centrifugal pcmps such as are used, for example, for circulating cooling Water through steam condensers, are principally air borne, structure borne, and water borne. Such sounds arise from and through mechanical vibration, bearings, rubbing surfaces and water pressure pulsations. The present invention is for decreasing noise levels in all of these categories, but principally for reducing the amplitude of water pressure pulsations generated within the pump.

The water pressure pulsations are due principally to (a) cavitation, (b) impact of water jets from the impeller striking the volute and shearing action at cutwater, (c) eddies and turbulence within the impeller, vo-lute and at cutwater, and (d) disturbances in film boundary layer' due to flow characteristics or irregularities.

Objects and features of the present invention are to reduce the noise due to any one or more of the above causes.

According to a preferred form of the invention, the casing of a centrifugal pump is made of a flexible soundabsorbing sheet material, such as fabric-reinforced rubber of the character used for automobile tires. To reinforce this inherently yieldable material, the casing is placed in a supporting jacket which may be made of a structurally rigid material, such as metal. The space between the jacket and casing is filled with a pressure-sustaining and distributing medium, such as a compressible liquid, gas under pressure, or non-resonant solid materials capable of dampening or of absorbing sounds.

Other objects and features of the invention will be more apparent from the following description when considered with the accompanying drawing in which:

Fig. l is a vertical section taken through a pump according to the invention;

Fig. 2 is a partial horizontal section taken on the line 22 of Fig. l; and

Fig. 3 is an elevation of the pump jacket showing the relative positions of the outside coupling flanges and of the intake and discharge passages of the centrifugal pump illustrated in Fig. 1.

In the following description and in the claims various details will be identified by specific names, for convenience, but they are intended to be as generic in their application as the art will permit.

Referring now to the drawing, the pump and its enclosing jacket will first be described briefly. The pump assembly comprises a flexible casing 119 in which an impeller 11 is mounted, and a jacket 12 with a balancing space 13 provided between the casing and the jacket for containing a balancing medium, as explained more fully below. When the drive shaft 16 drives the impeller 11 to run the pump, water flows in the directions of the arrows from intake conduit 23, 14, into an approximately circular intake chamber 17 and is discharged through a volute discharge chamber 18 and discharge conduit 15,

Patented Mar. 7, 1961 25, in the usual manner for the type of circulating centrifugal pump shown.

The jacket 12 comprises a base 21 to which is bolted a hollow body 22. Intake conduit 23 is bolted to the side wall of jacket 22 by a flange coupling 24, and dis charge conduit 25 is bolted to the same side wall by flange coupling 26. The jacket 12 is closed tightly, except for an opening to which pipe 27 is connected. Pipe 27 supplies the balancing liquid or gas to the space 13, as discussed more at length below. It will be understood that the jacket 12 may be made from any suitable structurally strong material, such as metal.

The top wall of jacket 12 has a bearing sleeve 30 secured thereto for journalling the shaft 31 to which is applied a protecting sleeve 32 rotatable with the shaft. The bearing is sealed by a stuffing box of conventional construction denoted generally by 33. Jacket 12 has a platform 35 which supports a prime mover 36 which may be an electric motor having a drive shaft 16. The shaft 16 drives shaft 31 through a suitable coupling 37.

The flexible casing 10 of the centrifugal pump will now be described more in detail. The casing 10 is made of a flexible sound-absorbing and dampening sheet material, such as reinforced rubber or rubber-like material, preferably reinforced with a fabric in single or multiple plies, which may be incorporated into the rubber in a manner similar to that practiced in the manufacture of conventional automobile tires. In the drawing the reinforcing is denoted in general by 40.

As explained below, the casing is moulded in two sections of such configuration as to provide, particularly when assembled and bolted in place in a rigid jacket, a pump casing of considerable structural stability without possessing the stiff and rigid characteristics of metal. The casing is essentially a sound-dampening sheet material having substantial tensile strength. By sheet material a material is meant that is relatively long and wide as compared to thickness, even though in places the material may be thickened, as at the hubs 60 and 63, for special purposes.

The main parts of the casing 10 comprise the intake chamber 17 to which intake conduit 14 is integrally con nected; volute discharge chamber 18 to which discharge conduit 15 is integrally connected; and supporting skirt 4.1. It will be noted that the integral connection of skirt 41 to the wall of discharge chamber 18 includes the reinforcing fabric 40. At least one ply of the fabric 40 extends from the wall of the chamber 17 into the skirt 41, as shown in Fig. l.

The intake chamber 17 is slightly eccentric with respect to the impeller axis and has an integral dividing wall or bafile 42 (Fig. 2) for equalizing the flow of intake water circumferentially around the impeller 11. Intake conduit 14' is secured to the vertical wall of jacket 12 by a flange coupling 43 integral with the wall of the intake chamber 17.

The discharge chamber 13 is in the form of a. volute having its enlarging end (as shown in broken lines) integrally connected with a discharge conduit 15 The conduit 15 is connected to a side wall of jacket 12 by a flange coupling 44-. The coupling flanges 43 and 44 are reinforced similarly to flange coupling 59, described below.

The supporting skirt 41 is made integral with the Wall of the volute chamber 18 and has an integral flange 50 which is bolted to the top wall of jacket 12. Skirt 41 has one or more openings indicated by 52 to allow for the passage of fluid balancing medium contained in the balancing space 13.

Thus, integral skirt 41, integral intake conduit 14 and integral discharge conduit 15 are all similarly connected to the jacket 12 and cooperate to support the pump casing in proper relationship with respect to the jacket 12 and within a surrounding balancing medium.

The intake chamber 17 and the discharge chamberls are parts of separately moulded sections which are joined together around the throat of the pump by a series of bolts 45 passing through a flange 46 on the outside of the intake chamber. The bolts 45 are engaged in nuts 47 embedded in bonded relationship in the wall of the discharge chamber. The bolts pass through a planar section of a metal ring 48 which has a cylindrical section at either side of the planar section and a conic section in the form of a diffuser 49 connected to the inner cylindrical section. The somewhat irregular cross-section of the ring 48 maintains the. circularity of the throat within the intake chamber part of the pump.

The impeller 11 may be of conventional metal construction. It comprises a hub 54 affixed to impeller shaft 53 in any conventional way. It has a series of vanes 55 which have clearance with the diffuser 49 lining the throat. It will be understood that the shape and number of the vanes is such as to draw waterfrom the intake chamber 17 and deliver it to the discharge chamber 18.

To provide a bearing in the pump casing for the impeller shaft, the wall of discharge chamber 18 is thickened to form a hub 60 Hub 60 carries a bearing sleeve 61 which journals a shaft sleeve 62 affixed to the impeller shaft 53. The wall of intake chamber 17 is similarly thickened to provide a hub 63 which carries a bearing sleeve 64 to journal a sleeve 65 affixed to impeller shaft 53.

The impeller shaft 53 may be connected to the driving shaft 31 through a flexible coupling of any' suitable type. As shown in Fig. 1, a universal, sound-absorbing joint 70 connects shaft 31 and impeller shaft 53. The joint 70 may have sound-absorbing bushings around its trunnions. The flexibility of the coupling permits a certain amount of yield of the flexible casing 10 with respect to the rigid jacket 12 and the transmittal of axial thrust along the shaft.

To yieldably support the surface of the pump casing 10, that is to say, to transmit water pressure from the surface of the casing 10 to the walls of the containing jacket 12, a gaseous medium is applied through pipe 27 to the balancing space 13. For many applications it will suflice to maintain the pressure of the gas in the balancing space 13 substantially equal to the water pressure in the intake chamber 17 of the centrifugal pump.

As has been made clear, an important feature of the invention is the use of a sound-absorbing or asounddampening material for the pump casing. As one example, automobile tire material has been given. This material is suitable to withstand the pressure differential between intake and discharge pressures used for circulating cooling water through the steam condensers of various power plant installations as, for example, where the diiferential pressure may be of the order of twenty pounds per square inch, more or less.

The pressure balancing medium or transfer material located between the casing and the jacket is preferably elastic, compressible and sound-absorbing. Both the casing material and transfer material should preferably be aperiodic, that is to say, these materials should have no natural period of vibration, However, it is suflicient if the materials have no natural period within the noise frequency range generated by the pumping action. Reference to sound or noise herein includes audible, sub-audio and supersonic frequencies.

If is obvious that the present pump may be used wherever it is desired to decrease noise amplitudes. One use of the invention is for pumps located below water level as for circulating cooling water through steam condensers in vessels. For this use it is convenient to connect the balancing chamber pipe 27 to a ships hull so as to subject the outside of the pump to the head of water corresponding to thelocation ofthe pump below water level. In this way the pressure in the balancing space 13 may be maintained substantially equal to the actual water pressure on the intake side of the pump. However, since water is not compressible and is not a particularly good soundabsorbing medium, it is preferred to trap air in the balancing space 13 and apply the pressure head to the air confined in the jacket 22. In this way water is excluded in whole or in part from the balancing space 13 so that the air may act as a cushion to absorb pressure pulsations as well as serve as a resilient support for the flexible pump casing.

It is obvious that the invention is susceptible of modifications. For example, the pump casing 10 may also be made of any suitable impermeable material having the sound-deadening characteristics of rubber, impregnated fabric, either of natural fiber or artificial fiber, and of other materials so long as the material is sound-dampening. Similarly, the balancing medium contained in the balancing space 13 may be gases other than air; it may be of compressible liquids; it may be compressible solids such as cork or sponge rubber so long as the materials contribute support to the pump casing and are sounddampening. Furthermore, to acoustically insulate the impeller shaft from drive shaft 31, the flexible coupling 70 may be replaced by other types of sound-absorbing flexible couplings, such as fabric universal joints, The invention may be applied to centrifugal pumps for liquids other than water and to centrifugal compressors for pumping gases.

While certain novel features of the invention have been disclosed herein, and are pointed out in the annexed claims, it will be understood that various omissions, substitutions and changes may be made by those skilled in the art without departing from the spirit of the invention.

What is claimed is: I

1. In a sound-dampening pump, a casing of flexible sound-absorbing sheet material, said casing having an intake chamber, a discharge chamber, a throat connecting said chambers, an impeller in said throat, means for driving said impeller to pump fluid from said intake chamber to said discharge chamber, an outer rigid jacket enclosing a chamber surrounding said casing, and a soundabsorbing balancing medium disposed in said chamber between said casing and said jacket to support said casing against pressure generated Within said casing.

2. In the pump of claim 1, said flexible sound-absorbing sheet material comprising rubber having fabric reinforcing. 7

3. In the pump of claim 1, said balancing medium comprising gas.

4. In the pump of claim 1, said drive means comprising an impeller shaft on which said impeller is mounted, said casing having a bearing for said impeller shaft, said jacket having a bearing, a drive shaft in said jacket bearing, and a flexible sound-absorbing coupling connecting said impeller shaft and drive shaft.

5. In'the pump of claim 1, said jacket having an intake conduit and a discharge conduit, said flexible casing having a flexible intake conduit integrally connected to said intake chamber of said casing, meansconnecting said intake conduits, said flexible casing having a flexible discharge conduit integrally connected to said discharge chamber of said casing, means connecting said discharge conduits, said flexible casing having a flexible supporting skirt integrally connected to said casing and surrounding said drive means, means connecting said skirt to said jacket.

6. In the pump of claim 1, said casing comprising two 8. In the pump of claim 1, said balancing medium comprising a compressible gas and a liquid.

9. In the pump of claim 1, said balancing medium comprising a compressible solid medium.

10. In a pump, a sound-dampening pump casing comprising walls of reinforced rubber-like material having interior and exterior wall surfaces, said interior wall surfaces defining a suction chamber, a discharge chamber, a throat connecting said chambers, an intake passage connecting with said suction chamber and a discharge passage connecting with said discharge chamber; a jacket for containing said casing and a fluid medium contiguous to said exterior wall surfaces and entirely surrounding said casing, said jacket having openings in communication with said intake and discharge passages for the transference of pumping liquid through a wall of said jacket to and from said casing; an impeller shaft journalled in said casing; means for driving said impeller shaft, said driving means including a shaft extending through a wall of said jacket and connections with said impeller shaft;

means supporting said casing within said jacket, said means comprising flanges integral with the material of said walls of said casing and devices for securing said flanges to said jacket, and means communicating with said chamber enclosed by said jacket whereby the pressure of the fluid medium surrounding said casing may be regulated.

References Cited in the file of this patent UNITED STATES PATENTS 1,591,939 Humphrey July 6, 1926 1,671,054 Welsh May 22, 1928 2,483,335 Davis Sept. 27, 1949 2,849,174 Spreng Aug. 26, 1958 FOREIGN PATENTS 102,207 Australia Oct. 6, 1937 

